Why is the ingestion of salt and water beneficial in dealing with coronary spasms?

Coronary spasms. To my knowledge, there is no relationship between ingesting salt and water and the relief of "coronary spasms".
It isn't. There's nothing special about salt water that helps coronary spasm. It is given intravenously to raise blood pressure when needed and given in tiny amounts routinely in the hospital to "keep the vein open" (kvo).